Proposal Title: The impact of social determinants, conditional cash transfers and primary health care on HIV/AIDS: an integrated retrospective and forecasting approach based on a cohort of 100 million Brazilians Project Summary Considerable progress has been made in controlling many aspects of the HIV/AIDS epidemic. But challenges remain in terms of scaling up successful national programs. This study will contribute to knowledge on the impact of large-scale initiatives addressing both the social and medical determinants of HIV/AIDS by combining data from Brazil?s national HIV/AIDS registry with other largescale databases including the ?100 Million Brazilian Cohort?: a virtual cohort of more than 100 million individuals over 18 years obtained by the linkage of large countrywide socioeconomic and health datasets. It will be the first study to follow such a large number of individuals over time and in non-experimental conditions to understand how social determinants, conditional cash transfers and primary health care affect HIV/AIDS incidence, hospitalization and mortality; and how receipt of social protections at the individual level affects HIV/AIDS outcomes (ART adherence and mortality). Thanks to the unprecedented dimension of the dataset and the methods proposed, we will assess impact heterogeneities of the two interventions in a large range of different subpopulations, as well as possible synergistic effects. Using the longitudinal aspect of the cohort we will explore and assess in depth expected and unexpected dynamics, lagged and long- term effects of changes in living conditions and in exposures to conditional cash transfers and community- based primary health care. We will then expand the cohort and integrate estimates from the retrospective evaluations with the development of forecasting for several alternative policy scenarios. Using an innovative joined microsimulation and agent-based model we will be able to forecast the effects of the current Brazilian economic crisis, overall and for several subpopulations, on the HIV/AIDS epidemic. We will forecast and compare the impact of a wide range of alternative policy scenarios, such as the maintenance of current levels of support of conditional cash transfer and primary care, reductions of coverage and benefits due to fiscal austerity measures, or expansion in different subpopulation and with different dynamics. We will calibrate and select the combinations of policy response able to maximize the benefits on the HIV/AIDS epidemic, even during an economic crisis. The empirical results and the innovative mathematical models produced in this project will represent an essential contribution to the understanding and control of HIV/AIDS in lower and middle income country settings, as well as for vulnerable populations in the United States.